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Message-ID: <4BB47EEA.4070102@redhat.com> Date: Thu, 01 Apr 2010 14:09:30 +0300 From: Avi Kivity <avi@...hat.com> To: Peter Zijlstra <peterz@...radead.org> CC: Rik van Riel <riel@...hat.com>, linux-kernel@...r.kernel.org, aarcange@...hat.com, akpm@...ux-foundation.org, Kent Overstreet <kent.overstreet@...il.com>, Ingo Molnar <mingo@...e.hu>, tglx <tglx@...utronix.de> Subject: Re: [COUNTERPATCH] mm: avoid overflowing preempt_count() in mmu_take_all_locks() On 04/01/2010 01:31 PM, Peter Zijlstra wrote: > I'm sure you dropped Ingo and Thomas by accident. > > On Thu, 2010-04-01 at 12:40 +0300, Avi Kivity wrote: > >> mmu_take_all_locks() takes a spinlock for each vma, which means we increase >> the preempt count by the number of vmas in an address space. Since the user >> controls the number of vmas, they can cause preempt_count to overflow. >> >> Fix by making mmu_take_all_locks() only disable preemption once by making >> the spinlocks preempt-neutral. >> > Right, so while this will get rid of the warning it doesn't make the > code any nicer, its still a massive !preempt latency spot. > True. But this is a band-aid we can apply now while the correct fix is being worked out. -- error compiling committee.c: too many arguments to function -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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